Latency / Ping / 延迟探测

NetworkDiagnostic.ping() measures round-trip time towards a target host and reports sent / received counts, packet loss, min/avg/max and jitter.

NetworkDiagnostic.ping() 测量到目标主机的往返时间，并给出发送/接收次数、丢包率、最小/平均/最大耗时与抖动。

Basic / 基础

final ping = await NetworkDiagnostic.ping(
  host: '1.1.1.1',
  count: 5,
  timeout: const Duration(seconds: 2),
  interval: const Duration(milliseconds: 200),
  port: 443,
);
 
print('received : ${ping.received}/${ping.sent}');
print('loss     : ${ping.packetLoss.toStringAsFixed(1)} %');
print('min/avg/max: ${ping.minTime.toStringAsFixed(1)} / '
      '${ping.averageTime.toStringAsFixed(1)} / '
      '${ping.maxTime.toStringAsFixed(1)} ms');
print('jitter   : ${ping.jitter.toStringAsFixed(2)} ms');
print('samples  : ${ping.times}');

Parameter	Default	Meaning
`host`	`config.pingHost`	Target host
`count`	`config.pingCount`	Number of probes
`timeout`	`config.pingTimeout`	Per-probe timeout
`interval`	`config.pingInterval`	Delay between probes
`port`	`config.pingPort`	TCP port probed in `PingMode.tcp`
`mode`	`PingMode.tcp`	`PingMode.tcp` or `PingMode.icmp`

TCP vs ICMP / TCP 与 ICMP

PingMode.tcp performs a TCP handshake to host:port — the portable equivalent of ICMP and the only mode available on Android/iOS.

PingMode.tcp 通过 TCP 握手到 host:port 测量往返，是移动端唯一可用的模式。

// Desktop only — falls back gracefully if the `ping` binary is unavailable.
await NetworkDiagnostic.ping(host: '1.1.1.1', count: 4, mode: PingMode.icmp);

ping.isSuccess is true when at least one probe answered; check it before trusting the averages.

至少一次成功响应时 isSuccess 为 true，读平均值前建议先判断它。

A TCP ping needs a listening port. Probing host with port: 443 fails if that host does not accept TCP/443 — that is “filtered”, not “offline”. Use mode: PingMode.icmp on desktop to get closer to real ICMP. TCP 探测需要一个在监听的端口。对不接受 TCP/443 的主机探测 port: 443 会失败—— 那是“被过滤”，不是“离线”。在桌面上用 PingMode.icmp 更接近真实 ICMP。

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